Pharm/Pain Flashcards
What is volume of distribution?
Theoretical volume in the body (fluids and tissues) in which the drug may be found after absorption
What is the concentration of the drug equal to?
Amount administered (dose)/The volume of distribution (Vd)
What is clearance?
Fraction of the drug that is cleared from the body in any given unit of time
Why is clearance important
Dictates how much of drug must be given and how often to maintain desired concentration in the body
What is bioavailability?
Amount of administered drug that actually reaches the blood
What 2 classes of drug decrease the bioavailability of calcium, magnesium, iron, and aluminum compounds?
Cephalosporins and Fluoroquinolones
If a drug is given IV, what is the bioavailability?
100%
If a drug is given PO, sublingual, PR, IM, SQ, ect… what 2 things determine its bioavailability?
- Host factors: Diet, illness, organ function
2. Drug factors: Whole, crushed, solution, injected
What are 2 reasons a drug concentraiton might be low?
- Bioavailability is low
2. Clearance is high
What is a lipophilic agent?
Bioavailability is enhanced by fatty foods
Name 2 drugs that are lopophilic and should be taken with fatty foods
- Istretinoin
2. Griseofulvin
What is half life?
The amount of time required for the concentration of the drug to decrease by half
After 1 half life, how much of the drug remains?
50%
After 2 half life, how much of the drug remains?
25%
After 3 half life, how much of the drug remains?
12.5%
After 4 half life, how much of the drug remains?
6.25%
After 5 half life, how much of the drug remains?
3.125%
After how many half-lives is approximately 97% of a drug cleared from the body?
5
What is steady state?
When a drug is administered at a constant interval and accumulates in the body so the amount in equals the amount out
Drug accumulation follows the same pattern as what?
Half-life clearance
After 5 half lives a drug reaches what % of steady state?
97%
When a dose or dosing interval changes, how many half lives are required to reach a new steady state?
5
What is absorption?
The progression of the drug from site of administration to the target sites
Name 3 reasons drugs administered PO are different in kids than adults
- Neonates and young infants have elevated gastric pH
- Neonates and young infants have delayed gastric emptying
- Proteins that are required for conversion from a pro-drug to a drug, and for drug transport, are expressed differently at different ages
What are some things which can change absorption or concentration of a drug?
- Crushing tabs into suspension
- Flavoring
- Mixing into formula or juice
What is distribution?
Where the drug disperses after it is absorbed into systemic circulation
What are two things that cause different distribution of drugs in kids (depending on whether they are hydrophilic or lipophilic)?
- Higher percentage of total body water
2. Lower body fat stores
What are 3 things which can affect the distribution of drugs?
- Serum levels of albumin
- Serum levels of other binding proteins
- Transporters
What is the primary organ for drug metabolism?
Liver
Name other organs which have drug-metabolizing enzymes besides the liver
Skin, kidney, GI tract, lungs
What are 3 drugs you can’t have dairy with because they are chelated by dairy products?
- Tetracycline
- Doxycycline
- Ciprofloxacin
What happens if you take an antiacid with an iron supplement?
It binds to the iron and prevents absorption increasing its elimination in the GI tract